The series can be loosely described as "SimCity in past civilizations with military and economic micromanagement". In the City Building Series the player is put in charge of providing goods and services to the populace of his town, ensuring crime is low, and reducing the risk of disease, fire and building collapse. The player must also strike a balance between imports, exports and taxes to keep his town financially strong. The player is also responsible for defending his town against invasion by building a military.

While the series visually changed from the first game (played from a bird's eye perspective set in a 320×200 256 color VGAresolution) to the last (playable up to 1280×1024), the basic mechanics remain the same and some aspects are common to all games.

The exception to this is Children of the Nile, which worked on a completely different system.

Some of these aspects differ considerably between games. For game-specific descriptions, please see the relevant game article.

A city's population is confined to housing plots designated on the map by the player. Empty plots are soon developed by arriving immigrants. Each house belongs to a discrete quality level which affects, among other things, the amount it pays in taxes to the city, and the number of residents it can accommodate. Initially, housing for new residents is of the most basic quality.

Houses will upgrade to the next quality level when the specific needs for their current level are met. This is called "housing evolution". These needs can be either commodities, services, or local desirability. The player is informed of the needs of any particular house, and so can act accordingly. Better overall housing quality benefits the city.

When houses reach a luxury quality level, their residents stop contributing to the city workforce. This can lead to labour shortages and industrial stagnation, so the player must be careful to ensure that some houses do not evolve past this threshold, even though the tax benefits are great. In later games, starting with Zeus, housing classes are separated. As a result, housing of a given class can only advance to the peak of that class's housing quality; to obtain luxury housing and tax-heavy aristocrats, it is instead necessary to establish elite housing plots for them to move into. In Caesar IV, the housings are further divided into two different classes of workers as well as the non-working elites.

The original model requires that buildings needing employees are sited close to where people live in order to establish a physical connection through walker contact. This mechanism is absent from Zeus onwards.

Some houses at particular housing quality levels require certain services before they can evolve to the next level.

Service is provided by service buildings; access to the buildings has evolved through the games. In the first few games, service was distributed by zone of effect, with access determined entirely by absolute distance to the facility. In later games, a service building employs a "walker". The walker will leave the service building and walk along connected roads, taking a random direction at every intersection. Eventually the walker will return to the service building directly, and the activity will repeat. As of Caesar IV, this was changed to a walking distance measure, whereby access is determined by the distance to the building following the roads; actual distance is irrelevant if the shortest route by road is still too long.

A house is said to be supplied by a particular service if the walker from that service has recently walked past the house. If a walker from the same service does not walk past again within a particular time frame, the house is no longer supplied by the service and may return to lower quality levels.

The particular services differ from game to game, but all operate under this principle.

Some houses at particular housing quality levels require certain commodities before they can evolve to the next level, just as they do services.

A commodity can be obtained by the city through industrial production, or trade. Some commodities require manufacture from a raw material which in turn must be obtained from the environment. Pottery in Pharaoh, for example, is manufactured at a Potter from Clay, which is obtained at a Clay Pit. If the city does not have local supplies of a raw material, it may be able to import it and then manufacture the finished product. Alternatively, it can import the finished product directly, but this is usually much more expensive than manufacturing the goods locally.

Commodities, when produced or imported, are stored in warehouses. From there they are distributed to retailers, which employ walkers. When a retailer walker walks past a house which requires a certain commodity, the house draws a small amount from the retailer's stockpile. This amount declines over time, and so is topped up every time the walker walks past, subject to availability.

If a house runs out of a particular commodity, it may devolve to lower quality levels.

Food is treated as a commodity, though there are some differences. Food comes in many different types, some with different sources. Most food can be produced on farms, but other food can be obtained through hunting and fishing. In most cases, food is stored at granaries instead of warehouses.

Houses at particular housing quality levels require a certain variety of foods before they can evolve to the next level. However, houses are not fastidious about which specific foods are supplied.

All industry is entirely state-controlled, with all employees being paid by the city treasury. Industry is necessary for the production of commodities. Industrial buildings must be connected to the city labour pool before they can become operational, which is done through a walker. When built, the industrial building will send out a walker along connected roads. If this walker passes occupied housing, the building is connected.

For a price, trade routes can be set up between cities. This allows the player to import commodities that may not be available in his or her city, or export for profit commodities that he is producing in excess. Different cities buy and sell different commodities, and these limitations are an integral aspect of the difficulty of particular campaign missions.

Trade can be conducted by land and water, and some cities only trade by one of these methods, further adding to the complexity.

Religion is a service, which employs priests at temples as walkers. However, religion also operates on another level. The player must ensure that the gods in his civilization's religion are appeased, and he is able to do so by making sure that the number of temples for each god is adequate for the city population, and ensuring that all houses are supplied by the religion service.

The precise mechanism by which this aspect of religion operates differs from game to game. In Zeus, the player builds massive temples called Sanctuaries, which are built like monuments, to honor the Gods. The God whom the player honors will then give great benefits onto the player's city so long as the sanctuary is staffed and given the necessary sacrifices of either food or animals. Each city could have a maximum of four Sanctuaries; the player was allowed to choose from a selection of the Greek pantheon. The player can pray to the god for aid or wait for the god to provide it directly. Foreign gods can also attack your city or release disasters on it.

In Caesar III, the player has to build temples as the population grows. A particular god will be pleased with a number of temples for a long time provided that the population does not grow, but when it does, it expects from the player to increase the number of temples.

In Emperor: Rise of the Middle Kingdom, the player has to give gifts to "Heroes"; if they are pleased enough, they will visit the city, provide benefits such as reduction in building costs, and walk around. There are four groups of Heroes: the Ancestral Heroes, the Daoist Heroes, the Confucian Heroes, and the Buddhist Heroes. Failure to keep the Ancestral Heroes content can result in disasters like earthquakes or floods.

In Pharaoh the player's city has a patron god and several local gods who must all be appeased. This is done by constructing unmanned shrines for minor coverage, staffed temples to provide citizen access to religion, and temple complexes for additional benefits. Festivals can be held to increase favor with one god. Pleased gods will grant miracles, such as extra goods or production speed, while displeased gods will cause disasters, such as the collapse of buildings or plague.

While the focus of the city resides on infrastructure building, in some maps the players are forced to keep a strong military, either for defense or conquer other cities. Military units are created at forts, and require weapons and other goods (like wood or horses), depending on the unit. In Zeus, the larger part of the army is composed by common citizens, and calling for war will have them leaving the city and their jobs. In both Zeus and Emperor: Rise of the Middle Kingdom the number of army units that are possible to build depends on the number of elite houses.

It is also possible to build defense structures, such as walls, gates, and towers.